CN107815587B - The high tube steel of fatigue resistance, its manufacturing method and the welded still pipe using it - Google Patents

The high tube steel of fatigue resistance, its manufacturing method and the welded still pipe using it Download PDF

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CN107815587B
CN107815587B CN201710818766.4A CN201710818766A CN107815587B CN 107815587 B CN107815587 B CN 107815587B CN 201710818766 A CN201710818766 A CN 201710818766A CN 107815587 B CN107815587 B CN 107815587B
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steel
temperature
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steel plate
content
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CN107815587A (en
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卢炅民
朱敏成
金基锡
金英薰
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Posco Holdings Inc
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Posco Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/008—Heat treatment of ferrous alloys containing Si
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/10—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies
    • C21D8/105—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of tubular bodies of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L9/00—Rigid pipes
    • F16L9/02—Rigid pipes of metal
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
    • C21D8/0226—Hot rolling

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacturing & Machinery (AREA)
  • General Engineering & Computer Science (AREA)
  • Heat Treatment Of Steel (AREA)

Abstract

The present invention provides the tube steels in a kind of application taken for such as oil or air lift.Particularly, a kind of tube steel with high antifatigue, the manufacturing method of the steel and the welded still pipe that obtains using the steel are provided.

Description

The high tube steel of fatigue resistance, its manufacturing method and the welded still pipe using it
Cross reference to related applications
This application claims submitted in September in 2016 12nd to Korean Intellectual Property Office application No. is 10-2016- The equity of the priority of 0117505 South Korea patent application, the entire disclosure are incorporated herein by reference.
Technical field
This disclosure relates to the tube steel in a kind of application taken for such as oil or air lift, more specifically it relates to a kind of tool There are the tube steel of high antifatigue, the manufacturing method of the steel and the welded still pipe obtained using the steel.
Background technique
In recent years, the environment for developing oil well and gas well (hereafter referred to collectively as oil well) becomes increasingly harsher, then positive effort Production cost is reduced, to improve rate of return (RMT).
Coiled tubing (coiled tubing) refer to outer diameter about 20mm to about 100mm and length greater than 1km wound on Welded pipe on spool.During operation, oil well is unlocked from spool and be inserted into coiled tubing, after operation, coiled tubing weight It is wound on spool.
Coiled tubing is a kind of product manufactured by the following method, wherein the tubulation steel obtained by cutting coils of hot-rolled steel Plate (skelp) is welded into long length, is formed and is managed by resistance welding, and so as to water pipe on big spool Mode carry out using, due to be pre-formed this length be several kilometers (km) coiled tubing, so the set-up time may It can reduce.Therefore, the demand of coiled tubing is gradually increased.
It is wrapped on spool due to coiled tubing and is unlocked from spool repeatedly, so the material for coiled tubing needs With good surface characteristic and high antifatigue.
Additionally, it is important that welding region of the control for the material of coiled tubing, lacks because if welding region has Intensity sunken or more lower than base metal may be then broken since stress collection neutralizes fatigue accumulation.
(patent document 1) Korean Patent Application Publication the 2014-0104497th
Summary of the invention
The aspect of the disclosure can be provided with the comparable intensity of intensity with API 5ST CT90 and equally with highly resistance The tube steel of fatigability, the manufacturing method of the steel and the welded still pipe by welding steel acquisition.
According to one aspect of the disclosure, the tube steel with high antifatigue may include: based on wt%, carbon (C): 0.10% to 0.15%, silicon (Si): 0.30% to 0.50%, manganese (Mn): 0.8% to 1.2%, phosphorus (P): 0.025% hereinafter, sulphur (S): 0.005% hereinafter, niobium (Nb): 0.01% to 0.03%, chromium (Cr): 0.5% to 0.7%, titanium (Ti): 0.01% to 0.03%, copper (Cu): 0.1% to 0.4%, nickel (Ni): 0.1% to 0.3%, nitrogen (N): 0.008% hereinafter, surplus is iron (Fe) With inevitable impurity, wherein chromium (Cr), copper (Cu) and nickel (Ni) can satisfy following formula, and steel can have including Partial size is the metallographic structure of 10 μm of ferrite and pearlites below.
[formula]
80<100(Cu+Ni+Cr)+(610-CT)<120
Wherein Cu, Ni and Cr respectively refer to the content of Cu, Ni and Cr by weight, and CT refers to coiling temperature (DEG C).
According to another aspect of the present disclosure, it may include: system that a kind of manufacture, which has the method for the tube steel of high antifatigue, The standby steel billet with above-mentioned alloying component；Steel billet is heated to the temperature within the scope of 1100 DEG C to 1300 DEG C；Extremely at 900 DEG C Roughing is carried out to reheating steel billet at a temperature in the range of 1100 DEG C；After roughing, at a temperature in the range of 800 DEG C to 900 DEG C Hot finishing is carried out to steel billet, to produce hot rolled steel plate；And after the cooling hot rolled steel plate, temperature is batched meet above-mentioned formula Steel plate is batched under degree (CT).
According to another aspect of the present disclosure, providing one kind has high antifatigue and is obtained by forming and welding steel Welded still pipe.
Specific embodiment
The present inventor is to the material improved suitable for taking the increasingly increased coiled tubing of demand for oil or air lift Physical property is studied.Particularly, it is intended to which providing, there are satisfactory fatigue properties to be manufactured to welding steel simultaneously With the comparable intensity of intensity with API 5ST CT90, (yield strength is 620MPa to 689MPa, and tensile strength is after pipe 669Mpa or more) tube steel.
As a result, it has been found by the present inventors that other than optimized alloy element and manufacturing condition, by optimization to tired special Property influential element-specific and manufacturing condition between relationship the tube steel with expected physical property can also be provided.It is based on The knowledge, the present inventor have invented the present invention.
It will be described in embodiment of the disclosure now.
According to one aspect of the disclosure, the tube steel with high antifatigue can have comprising alloying component below: Based on wt%, carbon (C): 0.10% to 0.15%, silicon (Si): 0.30% to 0.50%, manganese (Mn): 0.8% to 1.2%, phosphorus (P): 0.025% hereinafter, sulphur (S): 0.005% hereinafter, niobium (Nb): 0.01% to 0.03%, chromium (Cr): and 0.5% to 0.7%, Titanium (Ti): 0.01% to 0.03%, copper (Cu): 0.1% to 0.4%, nickel (Ni): 0.1% to 0.3% and nitrogen (N): 0.008% or less.
Hereinafter, it will be described in the reason of limiting the alloying component of tube steel above disclosured.Under In the description in face, unless otherwise stated, the content of each element is provided with wt%.
Carbon (C): 0.10% to 0.15%
Carbon (C) is the element for improving the harden ability of steel.If the content of carbon (C) is less than 0.10%, harden ability cannot fill Divide and improve, and therefore cannot be guaranteed expected intensity in the disclosure.On the contrary, being surrendered if the content of carbon (C) is more than 0.15% Intensity is excessively increased, this may make it difficult to carry out moulding process and may be decreased fatigue resistance.
Therefore, according to the disclosure, preferably the content of carbon (C) can be adjusted in the range of 0.10% to 0.15%.
Silicon (Si): 0.30% to 0.50%
Silicon (Si) increases the activity of carbon (C) in ferrite and promotes ferritic stabilization, to facilitate strong by being dissolved Change and carrys out proof strength.In addition, silicon (Si) forms such as Mn during resistance welding2SiO4Low melting point oxide so that It is easy that oxide is discharged during welding.
However, if there is cost problem less than 0.30% in steel-making in the content of silicon (Si), if silicon (Si's) contains Amount is more than 0.50%, then in addition to forming Mn2SiO4Except, it can also form a large amount of refractory oxide SiO2, thus in electric resistance welding The toughness of welding region is reduced during connecing.
Therefore, according to the disclosure, preferably the content of silicon (Si) can be adjusted in the range of 0.30% to 0.50%.
Mn (manganese): 0.8% to 1.2%
Manganese (Mn) is the element for effectively strengthening steel by solution strengthening.It, can be with when the content of manganese (Mn) is 0.8% or more The effect of harden ability enhancing is obtained, and can guarantee expected strength level in the disclosure.However, if the content of manganese (Mn) More than 1.2%, then the central part of the steel billet formed in steelmaking process by casting is formed in a thickness direction significantly Segregation zones, and the fatigue resistance of final products reduces.
Therefore, according to the disclosure, preferably the content of manganese (Mn) is adjusted in the range of 0.8% to 1.2%.
0.025% or less phosphorus (P):
Phosphorus (P) is the impurity being inevitably present in steel and the toughness for reducing steel, therefore lower phosphorus (P) content It is advantageous.However, the content of phosphorus (P) can be adjusted to 0.025% or less due to the cost in steelmaking process.
0.005% or less sulphur (S):
Sulphur (S) is the element for being likely to form coarse field trash and leading to toughness reduction and crack propagation, therefore can be by sulphur (S) Content be adjusted to as low as possible.However, due to the cost in steelmaking process, the content of sulphur (S) can be adjusted to 0.005% with Under.It is highly preferred that 0.002% or less can be adjusted to the content of sulphur (S).
Niobium (Nb): 0.01% to 0.03%
Niobium (Nb) is that have the element significantly affected to the intensity of steel by forming precipitate.Niobium (Nb) in steel by analysing Carbonitride or cause the solution strengthening in iron (Fe) out to improve the intensity of steel.Particularly, during steel billet reheats, Nb The dissolution of base precipitate, is then imperceptibly precipitated, in the hot rolling to effectively improve the intensity of steel.
However, if the content of niobium (Nb) may not be able to be adequately formed fine precipitate, therefore less than 0.01% Possibly expected strength level in the disclosure can not be obtained.On the contrary, if the content of niobium (Nb) is more than 0.03%, manufacturing cost It can increase.
Therefore, according to the disclosure, preferably the content of niobium (Nb) is adjusted in the range of 0.01% to 0.03%.
Chromium (Cr): 0.5% to 0.7%
Chromium (Cr) is the element for improving harden ability and corrosion resistance.If the content of chromium (Cr) is less than 0.5%, by adding Add chromium (Cr) that may not be able to sufficiently obtain the effect for improving corrosion resistance.On the contrary, if the content of chromium (Cr) is more than 0.7%, Weldability can significantly reduce.
Therefore, according to the disclosure, preferably the content of chromium (Cr) can be adjusted in the range of 0.5% to 0.7%.
Titanium (Ti): 0.01% to 0.03%
Titanium (Ti) with nitrogen (N) by reacting to form TiN, to inhibit welding heat affected zone (HAZ) during reheating And in steel billet austenite grain growth, to improve the intensity of steel.
For this purpose, titanium (Ti) can be added with the amount greater than 3.4 × N (wt%), i.e., preferably it is added with 0.01% or more amount. However, if the amount of titanium (Ti) is excessive, toughness may due to TiN etc. coarsening and reduce, the content of titanium (Ti) The upper limit is preferably set as 0.03%.
Copper (Cu): 0.1% to 0.4%
Copper (Cu) is effective in terms of improving the harden ability and corrosion resistance of base metal or welding region.However, such as The content of fruit copper (Cu) is then likely difficult to guarantee corrosion resistance less than 0.1%.On the contrary, if the content of copper (Cu) is more than 0.4%, then manufacturing cost can increase, therefore be economically worthless.
Therefore, according to the disclosure, preferably the content of copper (Cu) can be adjusted in the range of 0.1% to 0.4%.
Nickel (Ni): 0.1% to 0.3%
Nickel (Ni) is the element for being effectively improved harden ability and corrosion resistance.In addition, when nickel (Ni) is added together with copper (Cu) When, nickel (Ni) reacts with copper (Cu) and hinders to be formed low melting-point coper (Cu) phase, to inhibit the shape of the crackle in hot procedure At.In addition, nickel (Ni) can effectively improve the toughness of base metal.
In order to obtain said effect, the nickel (Ni) of the amount of 0.1% or more addition.However, since nickel (Ni) is expensive member Element, so the nickel (Ni) that addition is more than 0.3% is economically worthless.
Therefore, according to the disclosure, preferably the content of nickel (Ni) can be adjusted in the range of 0.1% to 0.3%.
Nitrogen (N): 0.008% or less (being free of 0%)
Nitrogen (N) is in conjunction with the element of such as titanium (Ti) or aluminium (Al) in steel and the element of fixed such as nitride.However, If the content of nitrogen (N) is more than 0.008%, these further amounts of elements are inevitably added.
Therefore, according to the disclosure, preferably the content of nitrogen (N) can be adjusted in the range below 0.008%.
In the disclosure, other ingredients are iron (Fe) and inevitable impurity.However, in the scope of the present invention or idea It is interior that other alloying elements can be added.
For example, other than above-mentioned alloying element, can also in addition add molybdenum (Mo) according to the disclosure.
Specifically, molybdenum (Mo) is the element for significantly improving harden ability, not only contributes to the intensity for improving steel, and be conducive to Improve the fatigue resistance of steel.However, molybdenum (Mo) is expensive element, so if a large amount of additions, then manufacturing cost can be can increase. Therefore, preferably the content of molybdenum (Mo) can be adjusted in the range below 0.2%.
According to the disclosure, the tube steel with mentioned component, which can satisfy, is expressed below copper (Cu), nickel (Ni) and chromium (Cr) Between relationship formula,
[formula]
80<100(Cu+Ni+Cr)+(610-CT)<120
(wherein Cu, Ni and Cr respectively refer to the content of Cu, Ni and Cr by weight, and CT indicates coiling temperature (DEG C)).
All elements, copper (Cu), nickel (Ni) and chromium (Cr) are all effective in terms of the fatigue resistance for improving steel.If The content of these elements is low, then possibly can not obtain expected strength level, and therefore may need to significantly reduce coiling temperature. On the contrary, may need to improve coiling temperature if the content of these elements is excessive.
As described below, if coiling temperature deviates a certain range, expected metallographic structure may not be able to be obtained.
Therefore, copper (Cu), nickel (Ni) and chromium (Cr) can be controlled within the scope of the coiling temperature of proposition to meet above-mentioned pass System.
The tube steel of the invention for meeting the relationship of above-mentioned alloying component and ingredient can have comprising ferrite and pearly-lustre The compound phase metallographic structure of body.
Preferably, ferritic partial size can be 10 μm or less.If ferritic partial size is more than 10 μm, may be easy The fatigue diffusion to crystal boundary occurs, it is thus possible to be difficult to ensure fatigue resistance.Partial size refers to equivalent circle diameter.
More specifically, the metallographic structure of preferably steel includes the ferrite and area fraction that area fraction is 50% to 80% For 20% to 50% pearlite.Since pearlite mutually more effectively inhibits fatigue diffusion than other, so preferable pearlite Area fraction in 20% or more range.However, since the upper limit of the content of the carbon (C) in the alloying component of the disclosure is 0.15wt%, it is possible to form pearlite up to 50 area %.
Hereinafter, description manufacture according to another aspect of the present disclosure is had to the method for the tube steel of high antifatigue.
According to the disclosure, there can be the steel billet of the relationship of the alloying component and ingredient that propose in the disclosure by preparing, And reheating process, course of hot rolling, cooling procedure and coiling process are carried out to steel billet to manufacture tube steel.Hereinafter, will Each process is described in detail.
[reheating process]
Reheating process is to heat steel successfully to carry out the subsequent operation of rolling and obtain the physical property of expected steel plate Process, for this purpose, carrying out reheating process within the scope of appropriate temperature.
In the disclosure, preferable reheating process carries out at a temperature in the range of 1100 DEG C to 1300 DEG C.If again Heating temperature is lower than 1100 DEG C, then is likely difficult to fully dissolve niobium (Nb), and therefore, it is difficult to obtain enough intensity.On the contrary, If relation reheating temperature is higher than 1300 DEG C, initial grain may be excessively coarse, it is thus possible to be difficult to refine crystal grain.
[course of hot rolling]
Roughing and hot finishing can be carried out to the steel billet reheated as described above to manufacture hot rolled steel plate.
At this point, preferably carrying out roughing at a temperature in the range of 900 DEG C to 1100 DEG C.If roughing is being lower than 900 DEG C At a temperature of complete, then the risk of the loading problem of rolling equipment may will increase.
After roughing, heat essence is preferably carried out at a temperature in the range of amorphization temperature range i.e. 800 DEG C are to 900 DEG C It rolls.If lower than 800 DEG C at a temperature of carry out hot finishing, exist the failure as caused by rolling load risk.On the contrary, If higher than 900 DEG C at a temperature of carry out hot finishing, coarse metallographic structure may be ultimately formed, and therefore possibly can not Guarantee expected intensity.
Therefore, according to the disclosure, during hot rolling, preferably roughing temperature is adjusted in 900 DEG C to 1100 DEG C ranges It is interior, hot finishing temperature is adjusted within the scope of 800 DEG C to 900 DEG C.
[cooling procedure and coiling process]
The hot rolled steel plate produced as described above can be cooled down and be batched.
It is cooled down to improve the intensity of steel plate and toughness.With the increase of cooling rate, due to the internal structure of steel plate In crystal grain refinement, the toughness of steel plate improves, and due to the development of the hard phase in the internal structure of steel plate, the intensity of steel plate It improves.
According to the disclosure, preferably cooling rate can be adjusted in the range of 50 DEG C/s or less.If cooling rate More than 50 DEG C/s, then the low-temperature phase of such as bainite may in a disguised form increase, it is thus possible to which it is horizontal higher than expected that there are possibility acquisitions Intensity or anti-fatigue performance may be decreased it is high a possibility that.In this case, although the lower limit of cooling rate is unlimited In particular value, but preferably, cooling rate is 10 DEG C/s or more.
In addition, cooling may proceed to coiling temperature.It, can be in the coiling temperature for meeting above-mentioned formula according to the disclosure (CT) it is batched under, to obtain the tube steel with satisfactory fatigue properties.
Preferably, coiling temperature can be within the scope of 590 DEG C to 630 DEG C.If coiling temperature is lower than 590 DEG C, can office The low-temperature phase that portion forms such as bainite is covert, and stress may be concentrated, to reduce fatigue resistance.On the contrary, if volume Taking temperature is more than 630 DEG C, then the size of pearlite particle may be excessively increased, therefore fatigue resistance may be decreased.
The hot rolled steel plate that produces as described above can be used to manufacture welded still pipe.For example, pickled hot steel can be passed through Plate with from the surface of hot rolled steel plate except descale, hot rolled steel plate is cut into scheduled width and to the hot rolled steel plate of cutting into Row tubulation process manufactures coiled tubing.
The manufacturing method of welded still pipe does not limit.It is, for example, possible to use the resistance welding method of high financial profit.Resistance Welding can carry out by any method.That is, resistance welding is not limited to specific method.
Can have expected physical property according to the welded still pipe that the disclosure obtains: yield strength be 620MPa extremely 689MPa, tensile strength are 669Mpa or more, and fatigue life is 1000 or more, and may adapt to coiled tubing.
Hereinafter, the disclosure will be more specifically described according to example.But following example should be only in descriptive sense It pays attention to, rather than the purpose for limitation.The scope of the present invention is defined by the following claims, and can thus rationally It modifies and changes in ground.
(example)
Under the conditions of shown in the following table 2, the steel billet with alloying component shown in the following table 1 is reheated, hot finishing, It cools down and batches to manufacture hot rolled steel plate.
The metallographic structure of each hot rolled steel plate is observed, the results are shown in the following table 3.
Then, tubulation process is resistance welded to the hot rolled steel plate, then measures its yield strength and tensile strength.It surveys Amount result is shown in the following table 3.It is carried out when test according to conventional ASTM A370.
In addition, fatigue life is measured by tensile and compression test, wherein production (facture) time fatigue will be set as The standard in service life.When measuring fatigue life, straining is 0.9%.Measurement result is also shown in table 3.
Table 1
* IS: * * CS: steel of the present invention compares steel
Table 2
* IS: * * CS: steel of the present invention compares steel
(after reheating, carrying out roughing at a temperature in the range of 900 DEG C to 1100 DEG C)
Table 3
* IS: * * CS: steel of the present invention compares steel
(in table 3, " F " indicates that ferrite, " P " indicate that pearlite, " B " indicate that bainite, " M " indicate martensite)
As shown in table 1 to table 3, the invention steel 1 to 3 for meeting the alloying component and manufacturing condition that propose in the disclosure is being made There is the high fatigue life in 1000 or more range after causing welded still pipe.
However, the comparison steel 1 to 6 for being unsatisfactory for the alloying component proposed in the disclosure and manufacturing condition is coarse due to being formed Metallographic structure or low-temperature phase in a disguised form have poor fatigue life.
As described above, the disclosure can provide a kind of tube steel, even if being manufactured by moulding process and welding procedure After steel pipe, which also not only has the intensity for being equal to API 5ST CT90, but also has high antifatigue.
The welded still pipe of the disclosure obtained and forming and welding steel is applicable to coiled tubing.

Claims (6)

1. a kind of tube steel with high antifatigue, the ladle contain: in terms of wt%, carbon, that is, C:0.10% to 0.15%, silicon That is Si:0.30% to 0.50%, manganese, that is, Mn:0.8% to 1.2%, phosphorus, that is, P:0.025% hereinafter, sulphur, that is, S:0.005% hereinafter, Niobium, that is, Nb:0.01% to 0.03%, chromium, that is, Cr:0.5% to 0.7%, titanium, that is, Ti:0.01% to 0.03%, copper, that is, Cu:0.1% To 0.4%, nickel, that is, Ni:0.1% to 0.3%, nitrogen, that is, N:0.008% hereinafter, surplus is iron, that is, Fe and inevitable impurity, Middle chromium, that is, Cr, copper, that is, Cu and nickel, that is, Ni meet following formula, and
It is ferrite that 10 μm of area fractions below are 50% to 80% comprising partial size that the steel, which has, and area fraction is The metallographic structure of 20% to 50% pearlite,
[formula]
80<100(Cu+Ni+Cr)+(610-CT)<120
Wherein, Cu, Ni and Cr respectively refer to the content of Cu, Ni and Cr by weight, and CT refers to coiling temperature (DEG C).
2. steel according to claim 1 further includes the molybdenum i.e. Mo of 0.2% amount below.
3. a kind of method that manufacture has the tube steel of high antifatigue, which comprises
Preparation includes steel billet below: based on wt%, carbon, that is, C:0.10% to 0.15%, silicon, that is, Si:0.30% to 0.50%, and manganese That is Mn:0.8% to 1.2%, phosphorus, that is, P:0.025% hereinafter, sulphur, that is, S:0.005% hereinafter, niobium, that is, Nb:0.01% to 0.03%, Chromium, that is, Cr:0.5% to 0.7%, titanium, that is, Ti:0.01% to 0.03%, copper, that is, Cu:0.1% to 0.4%, nickel, that is, Ni:0.1% is extremely 0.3%, nitrogen, that is, N:0.008% are hereinafter, surplus is iron, that is, Fe and inevitable impurity；
The steel billet is heated to the temperature within the scope of 1100 DEG C to 1300 DEG C；
Roughing is carried out to the steel billet reheated at a temperature in the range of 900 DEG C to 1100 DEG C；
After the roughing, hot finishing is carried out to the steel billet at a temperature in the range of 800 DEG C to 900 DEG C, to produce hot-rolled steel Plate；And
After with the cooling hot rolled steel plate of 50 DEG C/s cooling rate below, in the coiling temperature for meeting following formula i.e. CT Under batch the steel plate,
[formula]
80<100(Cu+Ni+Cr)+(610-CT)<120
Wherein, Cu, Ni and Cr respectively refer to the content of Cu, Ni and Cr by weight, and CT refers to coiling temperature (DEG C).
4. according to the method described in claim 3, wherein, the steel plate batches at a temperature in the range of 590 DEG C to 630 DEG C It carries out.
5. according to the method described in claim 3, wherein, the steel plate further includes the molybdenum i.e. Mo of 0.2% amount below.
6. a kind of welded still pipe with high antifatigue, by the way that steel of any of claims 1 or 2 is formed and welded And obtain, wherein the yield strength of the welded still pipe is 620MPa to 689MPa, and tensile strength is 669MPa or more, fatigue Service life is 1000 or more.
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